The word “hegemony” comes from the Greek, hegeisthai, to lead. It has come to define the influence of one state over others. Used more extensively following World War I, and especially after World War II, it has been used to describe the position of the United States in world influence over other nations.
A leadership vacuum existed after WWI with the United States having to come in during the latter stages to save England. However, the U.S. pulled back from its position of leadership following that war, disarmed and adopted an attitude of isolation from world affairs and conflicts. The result was armed forces of 120,000 men, few ships and no air force to speak of.